tasks sticking at Queued

[mfh17]

i can raise tasks, but they stay at queued. the only success I've had is if I stop web2py, delete the scheduled_worker table and file, then restart web2py and scheduler. then it runs for around 2 mins, then stops running, and new tasks get an ‘error assign task’ row .

i also see, in logs, “rewrite or cast the expression” and “ UPDATE scheduler_worker SET worker_stat__tmp=worker_stats” but i cannot execute this in PGadmin